A study of the architecture of the yeast cell wall has led to the conclusion that a relatively minor component, beta(1 to 6)glucan, acts as a sort of glue, holding together other components of the wall. Direct chemical linkages of beta(1 to 3)glucan and to chitin have been found. beta(1 to 6)glucan is also attached to mannoprotein through a remnant of glycosylphosphatidylinositol anchor, the structure of which was ascertained. Together with the previous finding of a linkage between chitin and beta(1 to 3)glucan, these results suggest the existence of a building block of the cell wall consisting of different cross-linked components. Because complexes have been found that only contain some of the components, there appears to be variability between the cross-links in different parts of the wall. The cross-links probably enable the fungal cell wall to withstand the internal turgor pressure, and agents that interfere with their formation are potential antifungals. In a previous study, it was found that the small GTP-binding protein Rho1p is an essential subunit and regulator of beta(1 to 3)glucan synthase, the enzyme that catalyzes the synthesis of the major structural component of the cell wall. More recent results show that certain temperature-sensitive rho1 mutants arrest in the G1 phase of the cell cycle. This would suggest a new function for Rho1p that is presently under investigation. Chitin synthases are responsible for the formation of the yeast primary septum during cell division. By performing a series of nested deletions in the genes of yeast chitin synthases 1 and 2, it was shown that the non-homologous amino-terminal regions of the enzymes are not required for either activity or function. Deletion from both ends of the remaining homologous portions were deleterious for the enzymes. All fungal synthases whose sequence is known contain in the region showing high similarity the motif GlnArgArgArgTrp. In collaboration with the group of A. Duran and C. Roncero at the University of Salamanca, Spain, it has been shown that mutations in the arginine residues lead to loss of activity and function in all three yeast chitin synthases. Therefore, the common sequence could be an interesting target for an inhibitor.